This is another bird that has undergone a number of taxonomical revisions, but at present I think its called the White-headed Stilt (Himantopus leucocephalus) which separates into into a full species away from a number of other similar birds.
These birds were feeding in the area of Werribee Treatment Plant where the treated water is released into the bay. Due to somewhat elevated nutrient levels in the water this area can be a bit of a hot spot, there were a number of other waders (too distant to identify with much confidence) and a couple of a very small terms (Fairy/ Little?) feeding in the area as well.
The birds with the pale heads are younger birds. This species really does have remarkably long legs!
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